Apparatus for and Method of Controlling a Starting Operation to Restart an Engine

ABSTRACT

In an engine provided with a variable valve mechanism which varies an operating angle of an intake valve and a lift amount thereof, when an engine operation is automatically stopped after the establishment of an idling stop condition, the operating angle of the intake valve and the lift amount thereof are varied to be smaller, so that a load of the variable valve mechanism at an engine operation restarting time is low. Then, when the engine operation restarting is requested, a first explosion pressure is obtained by performing fuel injection and ignition on a cylinder stopped in an expansion stroke, so that the engine operation is started. Further, after a first intake stroke, the operating angle of the intake valve and the lift amount thereof are increased.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for and a method ofcontrolling a starting operation to restart an engine of which theoperation is stopped. More particularly, the present invention relatesto a technology for restarting an engine provided with a variable valvemechanism for varying opening characteristics of an engine valve, byigniting fuel in a combustion chamber of the engine in a state where theoperation of the engine is stopped.

2. Description of the Related Art

Japanese Laid-open (Kokai) Patent Application Publication No.2005-030236 discloses a vehicular control apparatus for automaticallystopping an operation of an engine if a condition for automaticallystopping the engine operation is established during idling of theengine, and for igniting fuel in a combustion chamber of the engine torestart the engine operation when a restarting condition of the engineis satisfied after the automatic stopping of the engine.

In case where the engine operation is restarted in a manner as describedabove, employing no starter motor, it is possible to raise a rate ofsuccess in restarting of an engine by increasing, as much as possible, atorque allowance which is a difference between a torque necessary forstarting a rotating motion of a crankshaft and a torque generated by theengine.

Therefore, with a conventional technology, an effort has been made forincreasing the torque generation from an engine by, for example,enhancing the combustion performance of the engine. However, it hasdeveloped that only enhancement of the combustion performance of anengine is unable to constantly achieve a high success rate in thestarting of an engine.

On the other hand, as a method of increasing the afore-mentioned torqueallowance, there has been proposed a method of lowering engine frictionto thereby reduce the torque necessary for starting the rotating motionof a crankshaft. Nevertheless, there has been hitherto proposed nomeasure that can achieve such an effective lowering of engine frictionas is able to contribute greatly to a rise in the rate of success inrestating of the engine.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to raise a success ratein restarting of an engine operation through a reduction in a torquenecessary for driving a rotating motion of a crankshaft by lowering anengine friction, with an engine provided with a variable valvemechanism, which is provided for varying the opening characteristics ofan engine valve.

In order to achieve the above object, the present invention providessuch a novel technical concept that, when a fuel existing in acombustion chamber of an engine is ignited for restarting an engineoperation during stopping of the engine operation, a forcible reductionof a load that is applied by a variable valve mechanism is encouraged.

The other objects and features of this invention will become understoodfrom the following description with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically illustrating a generalconstruction of an engine embodying the present invention;

FIG. 2 is a perspective view illustrating a variable valve liftmechanism according to an embodiment of the present invention;

FIG. 3 is a side view, in part cross-section, of the variable valve liftmechanism according to the embodiment of the present invention;

FIG. 4 is a diagram illustrating a variable valve timing mechanismaccording to the embodiment of the present invention;

FIG. 5 is a flowchart illustrating a controlling process for anautomatic stopping of an engine operation according to the embodiment ofthe present invention;

FIG. 6 is a graphical view illustrating a correlation between anoperating angle of an intake valve and a lift amount thereof, and astarting torque for a crankshaft, according to the embodiment of thepresent invention;

FIG. 7 is a flowchart illustrating a controlling of an operation forrestarting an engine after the engine operation is automaticallystopped, according to the embodiment of the present invention;

FIG. 8 is a time chart illustrating a fuel injection timing, an ignitiontiming and an intake stroke at a time of restarting the operation of theengine according to the embodiment of the present invention; and,

FIG. 9 is a time chart illustrating behavior of an engine rotationnumber at the time of restarting the engine operation according to theembodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a block diagram illustrating a systematic construction of anengine for vehicle according to an embodiment of the present invention.

Referring to FIG. 1, an engine 101 is a typical internal combustionengine to which the present invention may be applied and comprised of aV-type six-cylinder engine provided with right and left banks, and thesame is an engine in which fuel is directly injected into each cylinderto be ignited by an ignition plug.

In an intake pipe 102 of engine 101, there is disposed an electronicallycontrolled throttle 104.

Air having passed though electronically controlled throttle 104 isdistributed to each bank and thereafter, is further distributed to eachof cylinders in each of the banks.

In each cylinder, suction of the air takes place into a combustionchamber 106 via an intake valve 105.

The gas having combusted in combustion chamber 106 in each cylinder isdischarged from combustion chamber 106 via an exhaust valve 107 andthereafter, flows together through each bank, to be purified by a frontcatalytic converter 108 a, 108 b and a rear catalytic converter 109 a,109 b, which are disposed in each bank.

The flows of the exhaust gas from each bank after being purified by rearcatalytic converter 109 a, 109 b enter together in a common exhaustpassage to thereby flow into a muffler 103, and is thereafter dischargedfrom muffler 103 into the atmosphere.

Exhaust valve 107 is driven by a cam axially supported on an exhaustcamshaft 110, to open or close under a fixed lift amount, a fixedoperating angle and a fixed valve timing.

On the other hand, a lift amount of intake valve 105, an operating anglethereof and a valve timing thereof on respective banks are variablycontrolled by variable valve lift mechanisms 112 a, 112 b and variablevalve timing mechanisms 113 a, 113 b, which constitute variable valvemechanisms disposed in respective banks.

Each of variable valve lift mechanisms 112 a, 112 b is a mechanism whichcontinuously varies the lift amount of intake valve 105 and theoperating angle thereof.

Further, each of variable valve timing mechanisms 113 a, 113 b is amechanism which continuously varies a phase of the center of theoperating angle of intake valve 105 by changing a rotating phase of anintake camshaft 3 relative to a crankshaft.

An electronic control unit (ECU) 114 incorporating therein amicrocomputer, sets a target intake air amount and a target intakenegative pressure according to engine operating conditions, and controlselectronically controlled throttle 104, variable valve lift mechanisms112 a and 112 b, and variable valve timing mechanisms 113 a and 113 b,based on the set target intake air amount and the set target intakenegative pressure.

Engine control unit 114 receives signals from various sensors, such asan air flow sensor 115 for detecting an amount of intake air flow ofengine 101, an accelerator sensor 116 for detecting a depression amountof an accelerator pedal, a crank angle sensor 117 for detecting arotating angle of the crankshaft, a throttle sensor 118 for detecting anopening TVO of electronically controlled throttle 104, a watertemperature sensor 119 for detecting a temperature of the cooling waterof engine 101, an air-fuel ratio sensor 111 a, 111 b disposed in eachbank for detecting an air-fuel ratio based on oxygen concentration inthe exhaust gas, a brake switch 120 which is turned ON when a foot brakeof a vehicle is operated, a vehicle speed sensor 121 for detecting avehicle speed.

Further, a fuel injection valve 131 is disposed for directly injectingfuel into combustion chamber 106 in a cylinder bore of each cylinder oneach bank. Furthermore, an ignition plug 122 is disposed on a topportion of each combustion chamber 106.

Next, there will be described the structure of each of variable valvelift mechanisms 112 a, 112 b, and the structure of each of variablevalve timing mechanisms 113 a, 113 b, with reference to FIGS. 2 through4.

In engine 101, a pair of intake valves 105, 105 is disposed for eachcylinder on each bank, and above intake valves 105, 105, an intakecamshaft 3 which is driven for rotation by the crankshaft of engine 101is rotatably supported so as to extend in a direction along a cylindertrain.

Swing cams 4, each of which is in contact with a valve lifter 2 a ofeach intake valve 105 for causing intake valve 105 to open or close, aremounted by fitting on an outer surface of intake camshaft 3, so as to berelatively rotatable with respect to intake camshaft 3.

Between intake camshaft 3 and swing cams 4, variable valve liftmechanism 112 a or 112 b which continuously varies the operating angleof intake valves 105 as well as the lift amount thereof, is disposed.

Further, on one end portion of intake camshaft 3 on each bank, there isdisposed variable valve timing mechanism 113 a or 113 b which changesthe rotating phase of intake camshaft 3 relative to the crankshaft tocontinuously vary the phase of the center of the operating angle of eachintake valve 105.

As shown in FIGS. 2 and 3, each of variable valve lift mechanisms 112 a,112 b includes: a drive cam 11 of circular shape which is fixedly andeccentrically mounted on intake camshaft 3; a link 12 of ring shapewhich is fitted to an outer surface of drive cam 11 to be rotatablerelative to drive cam 11; a control shaft 13 which extends in adirection of the cylinder train to be in approximately parallel withintake camshaft 3; a control cam 14 of circular shape which is fixedlyand eccentrically mounted on control shaft 13; a locker arm 15 which isfitted onto an outer surface of control cam 14 to be rotatable relativeto control cam 14, and has one end thereof connected to a tip end oflink 12 of ring shape; and a link 16 of rod shape which is disposed tobe connected to the other end of locker arm 15 and to swing cam 4.

Control shaft 13 is rotatably driven by an actuator 17 such as anelectric motor, via a gear train 18 to be rotated within a predeterminedangular range.

According to the above-mentioned configuration, when intake camshaft 3rotates in association with the crankshaft, ring shaped link 12 performsan approximately translational motion via drive cam 17, and also, lockerarm 15 swings about the center axis of control cam 14 while causingswing cams 4 to swing via rod shaped link 16, so that intake valves 105are driven to open or close.

Further, when control shaft 13 is changed in its rotating angle, theaxle center of control cam 14, which is the swing center of locker arm15, is changed in its position, and as a result, the orientation of eachswing cam 4 is changed.

Hence, the operating angle of each intake valve 105 and the lift amountthereof are continuously varied while the phase of the center of theoperating angle of each intake valve 105 being approximately fixed.

Incidentally, it may be possible to use variable valve lift mechanism112 a or 112 b having a different type of characteristics, in which whenthe valve operating angle and the valve lift amount of intake valve 105are varied, a variation in the phase of the center of the valveoperating angle per se simultaneously takes place.

FIG. 4 shows each of variable valve timing mechanisms 113 a, 113 b.

Each of variable valve timing mechanisms 113 a, 113 b is fixed to asprocket 25, which is rotated in synchronism with the crankshaft, andincludes: a first rotator 21 which is rotated together with sprocket 25;a second rotator 22 which is fixed to the one end of intake camshaft 3by means of a bolt 22 a, to be rotated together with intake camshaft 3;and an intermediate gear 23 of cylindrical shape which is engaged, viahelical splines 26, with an inner peripheral face of first rotator 21and with an outer peripheral face of second rotator 22.

Intermediate gear 23 is connected to a drum 27 via a thread screw 28,and a torsion spring 29 is disposed between drum 27 and intermediategear 23.

Intermediate gear 23 is urged by torsion spring 29 in a direction forcausing a change in the valve timing to be retarded (in the leftdirection in FIG. 4), and when a voltage is applied to anelectromagnetic retarder 24 for generating a magnetic force,intermediate gear 23 is moved in a direction for causing a change in thevalve timing to be advanced (in the right direction in FIG. 4), via themotion of drum 27 and thread screw 28.

A relative phase between rotators 21 and 22 is changed according to anaxial position of intermediate gear 23, so that the rotating phase ofintake camshaft 3 relative to the crankshaft is changed, and the phaseof the center of the operating angle of intake valve 105 is continuouslyvaried.

Actuator 17 comprised of e.g., an electric motor and electromagneticretarder 24 are controlled to be driven by control signals transmittedfrom electronic control unit 114.

Electronic control unit 114 capable of setting a target angle of controlshaft 13 performs a feedback control of an amount of operation ofactuator 17 so that an actual angle of control shaft 13 detected by anangle sensor 32 approaches the set target angle.

Further, electronic control unit 114 detects the rotating phase ofintake camshaft 3 relative to the crankshaft based on a signal from acam sensor 31 which outputs the signal at a reference angle position ofintake camshaft 3, and a signal from crank angle sensor 117 to therebyperform a feedback control of an amount of operation of electromagneticretarder 24, so that the detected result approaches a target rotatingphase.

Furthermore, electronic control unit 114 has an Idle-Stop-Start controlfunction for automatically stopping an operation of engine 101 when anautomatic operation stop condition is established during an idling stateof engine 101, and for automatically restarting the operation of engine101 when an operation restarting condition is established after theoperation of engine 101 has been automatically stopped.

By the above-described Idle-Stop-Start control function of theelectronic control unit 114, the operation of engine 101 isautomatically stopped, for example, in a state of waiting for the signalchange at a traffic intersection, to thereby intentionally aim areduction in fuel consumption as well as exhaust emission.

For restarting the operation of engine 101 by the Idle-Stop-Startcontrol function, it is required that restarting of the operation ofengine 101 occurs promptly in response to a starting operation performedby a driver. For this purpose, in place of the restarting by employing astarter motor, the operation of engine 101 is started by igniting thefuel in the combustion chamber in a state where the operation of engine101 is stopped, as described later.

A flowchart of FIG. 5 illustrates the details of the Idle-Stop-Startcontrol processed by electronic control unit 114.

In step S201, judgment is made as to whether or not a condition forautomatically stopping the operation of engine 101 is established.

Here, when the following conditions (1) through (5) are all established,it is judged that the condition for automatically stopping the operationof engine 101 is established.

-   (1) A vehicle speed is at 0 km/h.-   (2) The engine rotation number (rpm) is equal to or less than a    given reference rotation number.-   (3) Accelerator opening is closed to the full.-   (4) A brake switch 120 is turned ON.-   (5) The cooling water temperature is equal to or higher than a given    reference temperature.

For the above automatic operation stop condition, it is supposed thatthe operation of engine 101 is automatically stopped when a vehiclehalts and waits for the signal change at a traffic intersection in astate where engine 101 is completely warmed-up. However, it is notedthat the automatic operation stop condition is not limited to the above.

If the automatic operation stop condition is not established, thepresent controlling routine is terminated without proceeding to thesucceeding steps, and engine 101 continues to be operated.

On the other hand, if the automatic operation stop condition isestablished, the intake air amount of engine 101 and openingcharacteristics of intake valve 105 are controlled, before the operationof engine 101 is stopped.

Firstly, in step S202, electronically controlled throttle 104 is closedto an opening thereof at which the intake air amount required for idlingis obtained.

In next step S203, each of variable valve lift mechanisms 112 a, 112 bis controlled so that the operating angle of intake valve 105 and thelift amount thereof are at the maximum, and also, each of variable valvetiming mechanisms 113 a, 113 b is controlled so that the phase of thecenter of the operating angle of intake valve 105 is retarded to themost.

At this stage, it is to be understood that in a normal operation time,the intake air amount of engine 101 is controlled by varying the openingcharacteristics of respective intake valves 105 by variable valve liftmechanisms 112 a, 112 b and variable valve timing mechanisms 113 a, 113b, and the intake negative pressure is controlled by changing thethrottle opening by electronically controlled throttle 104.

To the contrary, the process in steps 8202 and S203 is executed byswitching to a state where the intake air amount and the intake negativepressure are controlled by electronically controlled throttle 104.Namely, by the process in step S202, variable valve lift mechanisms 112a, 112 b and variable valve timing mechanisms 113 a, 113 b arecontrolled so that the intake air amount is at the maximum, but by theprocess in step S203, the opening of electronically controlled throttle104 is made smaller so that the intake air amount is controlled tobecome that at an idling time.

In step 8204, the fuel injection by fuel injection valve 131 is stoppedand also the ignition by ignition plug 122 is stopped, so that theoperation of engine 101 is stopped.

In step S205, the opening of electronically controlled throttle 104,which has been made smaller so that the intake air amount of engine 101is controlled to be that at the idling time, is opened to the full whileengine 101 is inertially rotating.

Since the fuel injection and the ignition are stopped beforeelectronically controlled throttle 104 is opened to the full, torque ofengine 101 does not increase.

When the opening of electronically controlled throttle 104 is opened tothe full during engine 101 is inertially rotated after the fuelinjection and the ignition are stopped, since variable valve liftmechanisms 112 a, 112 b and variable valve timing mechanisms 113 a, 113b are controlled so that the intake air amount reaches the maximum,engine 101 sucks therein a lot of air.

Then, when engine 101 sucks therein a large amount of intake air, alarge amount of compression work takes place in each cylinder, andtherefore, one cylinder among six cylinders is permitted to stop itspiston motion at an approximately fixed position thereof during anexpansion stroke. It is to be noted that in the one cylinder in whichthe piston motion is stopped during the expansion stroke, confinement ofthe intake air within the cylinder occurs.

As described later, when the operation of engine 101 should berestarted, the fuel is injected to the cylinder in which the pistonmotion is stopped during the expansion stroke so as to cause ignitionand thus, the crankshaft starts to be rotated by an explosion pressureat that time. Accordingly, in order to restart the operation of engine101, it is necessary to stop one cylinder among six cylinders during theexpansion stroke.

Here, if a load applied while engine 101 is inertially rotating israther small, a braking force due to the compression work is weakenedresulting in that a piston is stopped at relatively retarded timingduring the expansion stroke. Then, when the motion of piston in theabove-mentioned one cylinder is stopped at the retarded timing duringthe expansion stroke thereof, a rotating force derived from thecombustion in the one cylinder must be reduced, and as a result,restarting performance is degraded.

Therefore, an increase in the intake air amount while engine 101 isinertially rotating is intended, so that one cylinder among sixcylinders is stopped in its piston motion at a position advanced as muchas possible during the expansion stroke.

In step S206, judgment is made based on the signal from crank anglesensor 117 as to whether or not the rotation of engine 101 is completelystopped.

If the rotation of engine 101 is completely stopped, the routineproceeds to step S207.

In step S207, for the purpose of restarting of engine 101,electronically controlled throttle 104 is closed to come to the openingthereof at which the intake air amount at the time of idling operationof the engine is obtained, and also, the operating angle of intake valve105 and the lift amount thereof controlled by variable valve liftmechanism 112 a or 112 b are controlled to become target values suitablefor automatic starting of an engine, i.e., engine 101.

The target values for the automatic starting of the engine are set to besmaller than those at the time of starting by employing the startermotor and also to be smaller than those required for continuing theoperation to restart engine 101. As a result, a load applied by variablevalve lift mechanisms 112 a, 112 b, in other words, a load due todriving of intake valves 105 to open, at the time of automatic startingof the engine, can be greatly lessened.

As shown in FIG. 8, an intake stroke during which each intake valve 105is driven at the above-mentioned target values for the automaticstarting of the engine is set only for first one cylinder among sixcylinders, and the combustion in this first one cylinder occurs at thefourth combustion among the combustions of the six cylinders. Bycontrolling the operating angle of intake valve 105 and the lift amountthereof to come to the target values for the automatic starting of theengine, the intake air amount of each cylinder is greatly reduced, andaccordingly, there is a possibility that the torque is not sufficientlygenerated during the fourth combustion. However, if the sufficienttorque can be generated in the succeeding combustions, engine 101 can besuccessfully restarted.

On the other hand, at the time of starting the engine, a work foropening intake valves 105 must be performed by a first explosionpressure. Thus, if a load for driving the opening of intake valves 105during a first intake stroke is high, an increase in the crankshaftrotation by the first explosion pressure is inhibited so that thestarting performance of the engine is greatly lowered.

Accordingly, in the first intake stroke at the time of executing theautomatic starting of the engine, it is desirable to avoid such asituation that consumption of a large part of energy by the firstexplosion occurs for driving the opening of intake valves 105 ratherthan for sucking the air of which the amount is enough for generating atorque. Therefore, by decreasing the load for driving the opening ofintake valves 105 in the first intake stroke, the automatic starting ofthe engine can be achieved at a high rate of success.

Thus, the values that are certainly smaller than the values required forcontinuing the starting of the engine, are set to become the targetvalues for the automatic starting of the engine, and the target valuesfor the automatic starting of the engine may be set at the minimum valveoperating angle and the minimum valve lift amount in variable valve liftmechanisms 112 a, 112 b, and further, the above-mentioned minimum valveoperating angle and minimum valve lift amount may be zero, respectively.

However, in case of an engine having lesser number cylinders such as afour-cylinder engine, of which combustion interval is longer than thatof the six-cylinder engine, a variation of the rotating speed thereofmay become large unless the combustion for generating torque isperformed sequentially from the beginning of the starting of the engineand as a result, the starting performance of the engine must bedegraded. Therefore, in such a case, taking into account a rise in therotation by the first explosion pressure, the afore-described targetvalues for the automatic starting of the engine are set so that asubstantial amount of air suctioned during the first intake stroke canbe ensured.

In the above automatic starting of the engine, since the crankshaftstarts to rotate by virtue of the fuel combustion in the combustionchamber, if the torque allowance is made larger by increasing therotational energy obtained by the first combustion or by lowering thefriction which consumes this rotational energy, engine 101 can berestarted by the automatic starting of the engine at a high probability.

Therefore, in order to perform the automatic starting of the engine in astate where the operating angle of intake valve 105 and the lift amountthereof are set smaller values, respectively, and the load of variablevalve lift mechanisms 112 a, 112 b is lessened, the valve operatingangle and the valve lift amount are forcibly set in advance, at the timeof stopping of the engine, to become smaller than those in the startingof the engine by employing the starter motor.

Each of variable valve lift mechanisms 112 a, 112 b transmits a drivingforce from the crankshaft to valve lifter 2 a of each intake valve 105by means of a complex mechanism. Therefore, as shown in FIG. 6, in thecase of a standard valve operating angle and a standard valve liftamount, a starting torque necessary for driving the crankshaft at thetime of the automatic starting of the engine becomes significantlylarger than that necessary for directly driving the operation of intakevalves 105 by the cams axially supported by the camshaft.

However, as shown in FIG. 6, by significantly decreasing the valveoperating angle and the valve lift amount, it is possible to reduce thestarting torque for the crankshaft to become lower than that necessaryfor directly driving intake valves 105 by the cam axially supported bythe camshaft.

Then, if the automatic starting of the engine is executed in the statewhere the starting torque for driving the crankshaft is intentionallyreduced, it is possible to start the engine rotation in good response assoon as the first combustion occurs, and therefore an improvement of thesuccess rate in the automatic starting of the engine can be achieved.

In step S208, the cylinder in which the expansion stroke of its pistonis stopped is stored as a specific cylinder on which the fuel injectionand the ignition are firstly performed at the time of restarting theengine.

Incidentally, during a time period in which engine 101 is stopped by theautomatic stopping operation, each of variable valve lift mechanisms 112a, 112 b is kept to maintain a state where the valve operating angle andthe valve lift amount are set at the target values for the automaticstarting of the engine, and is ready for a subsequent restarting of theengine.

Next, there will be described a controlling processed for an automaticstarting of the engine from the above automatic stopping state of theengine with reference to the flowchart of FIG. 7.

In step S301, judgment is made as to whether or not a condition for thestarting of the engine is established.

That is to say, it is judged that the condition for the starting of theengine is established, if any one of the following conditions (1)through (4) is satisfied.

-   (1) Brake switch 120 is turned OFF.-   (2) The accelerator opening is not yet closed to the full,-   (3) The continuation time for which the state of stopping of the    engine operation continues has exceeded a reference time period.-   (4) A battery voltage is equal to or less than a reference voltage.

At this stage, it should, however, be understood that the condition forthe starting of the engine is not limited to the above-listed items.

If the condition for the starting of the engine is satisfied, theroutine proceeds to step S302 where the fuel is injected to the cylinderstopped in the expansion stroke, which has been stored in step S208, andimmediately thereafter, the operation for ignition is executed.

In V-type six-cylinder engine 101, as shown in FIG. 8 for example, if itis assumed that the cylinder stopped in the expansion stroke is thesixth cylinder on the left bank, the fuel of a previously determinedamount is injected from fuel injection valve 131 into the combustionchamber of the sixth cylinder in response to a request for the startingof the engine, and also, spark ignition is performed by ignition plug122 of the sixth cylinder so that the previously injected fuel isignited for combustion.

Then, in the sixth cylinder, the piston is moved down by the explosionpressure due to the fuel combustion, and the crankshaft starts to rotateand therefore, the starting of engine 101 is commenced.

When the sixth cylinder is in the expansion stroke, the third cylinderon the right bank is in the intake stroke during which intake valves 106are opened. However, since the operating angle of intake valves 105 andthe lift amount thereof controlled by variable valve lift mechanisms 112a, 112 b on both banks, are controlled to be set at the target valuesfor the automatic starting of the engine, the load required for drivingthe opening of intake valves 105 of the third cylinder is suppressed tobe smaller.

Therefore, the starting torque necessary for starting the rotation ofthe crankshaft by means of the first explosion pressure in the sixthcylinder becomes smaller, and a rise in the rotating speed of thecrankshaft can takes place in good response to the first explosion. As aresult, it is possible to improve the rate of success in the automaticstarting of the engine (refer to FIG. 9).

In next step S303, the fuel injection and the ignition are performed ona cylinder which has been stopped in the compression stroke thereof.

In engine 101, the ignition is performed in succession in the order ofthe first cylinder→the second cylinder→the third cylinder→the fourthcylinder→the fifth cylinder→the sixth cylinder, and therefore, it caneasily confirm that which one of the cylinders has been stopped in thecompression stroke based on this ignition order and the stored data ofcylinder which is stopped in the expansion stroke.

In the example shown in FIG. 8, the first cylinder on the right bank isthe cylinder which has been stopped in the compression stroke, andaccordingly, after the fuel is injected to the sixth cylinder forignition, the fuel is injected to the first cylinder for ignitionthereof, to thereby cause the explosion combustion in the first cylindersubsequently after the explosion combustion in the sixth cylinder, sothat the crankshaft which has started to rotate by the explosionpressure in the sixth cylinder continues the rotation thereof and therotating speed of the crankshaft is further increased.

After the fuel injection and the ignition on the cylinder which has beestopped in the compression stroke, the fuel injection and the ignitionare performed according to the prescribed ignition order.

Incidentally, the timing for performing the fuel injection in theautomatic starting of the engine is determined to be in the intakestroke.

In step S304, judgment is made as to whether or not it is a timing forstarting a control which is executed for variably incrementing the valveoperating angle and the valve lift amount which are controlled byvariable valve lift mechanism 112 (112 a or 112 b) on the bank to whichthe cylinder stopped in the expansion stroke belongs, from the targetvalues for the automatic starting of the engine.

The operation angle of intake valves 105 and the lift amount thereof areforcibly lessened in order to reduce a load expended for driving theopening of intake valves 105 in the first intake stroke. However, insuch a case, since the amount of intake air is reduced, the sufficienttorque cannot be obtained. Therefore, if the amount of intake air isalso small in the next intake stroke, a reduction in the engine rotatingspeed takes place.

Therefore, for the second intake stroke from a start of the automaticstarting of the engine, it is necessary to set a larger valve operatingangle and a larger valve lift amount than the respective target valuesfor the automatic starting of the engine, so that the necessary andsufficient amount of suction of the intake air can be achieved.

Accordingly, taking a response delay of variable valve lift mechanisms112 into consideration, a point of time previous by a response delaytime to a starting time of the second intake stroke is set as the starttiming of controlling for variably incrementing the valve operatingangle and the valve lift amount from the target values for the automaticstarting of the engine.

However, at this stage, the above-mentioned start timing of controllingcan be set at a point of time when the cylinder stopped in thecompression stroke reaches the top dead center when the operation of theengine is automatically stopped, by which the operating angle of intakevalves 105 and the lift amount thereof are increased after the firstwork to do the compression stroke is finished.

If the variable increment of the valve operating angle and the valvelift amount are started from the point of time when the cylinder stoppedin the compression stroke reaches the top dead center, it is possible toprevent an occurrence of such an unpleasant state that the load expendedfor driving the opening of intake valves 105 increases during the firstcompression work and as a result, the rise in the engine rotating speedbecomes dull.

If a determination is made that the time started from the automaticstarting is at the starting timing of controlling, the routine proceedsto step S305, to start the controlling for variably incrementing thevalve operating angle and the valve lift amount controlled by variablevalve lift mechanism 112 (112 a or 112 b) on the bank to which thecylinder stopped in the expansion stroke belongs, from the target valuesfor the automatic starting of the engine toward values required forcontinuing the operation for the starting of the engine.

In step S306, judgment is made as to whether or not a certain delayperiod has elapsed since commencement of the controlling process of stepS305.

The above-mentioned certain delay period may be set at a fixed period oftime, but is preferably set at such a period of time in which therotation of an engine only for one stroke takes place.

Then, when judgment is made that the above-described delay period haselapsed, the routine proceeds to step S307, to start the control ofvariably incrementing the valve operating angle and the valve liftamount controlled by variable valve lift mechanism 112 on the bank towhich the cylinder stopped in the expansion stroke does not belong, fromthe target values for the automatic starting of the engine toward thevalues required for continuing the starting of the engine.

In the above-described automatic starting of the engine, the operatingangle of intake valves 105 and the lift amount thereof in the firstintake stroke after commencement of the starting of the engine operationare forcibly made smaller, so that the starting torque for thecrankshaft is reduced to thereby enhance the starting performance.However, from the second intake stroke, it is necessary to increase thevalve operating angle and the valve lift amount so that the intake airamount capable of continuing the starting of the engine can be obtained.

In the example shown in FIG. 8, the cylinder which is firstly in theintake stroke after commencement of the starting of the engine operationis the third cylinder on the right bank, and from the view point thatthe driving to open intake valves 105 in the large valve operating angleand the large lift amount is avoided in the first expansion stroke, itis necessary to reduce the operating angle of intake valve 105 and thelift amount thereof in the first intake stroke of the third cylinder.

However, for the fourth cylinder which is secondly in the intake stroke,it is necessary to ensure the intake air amount at which the engineoperation can be continued, rather than lessening the load expended fordriving the opening of intake valves 105. From this point, with the leftbank, the control for variably incrementing the valve operating angleand the valve lift amount may be started immediately after commencementof the starting of the engine operation.

However, if actuator 17 is operated before the first top dead center inorder to increase the valve operating angle and the valve lift amountwith the left bank, the crankshaft starts to rotate due to the firstexplosion combustion, to produce resistance against engine 101 in whichthe intake air amount in the first cylinder is being compressed, so thata rise in the engine rotating speed becomes dull.

Accordingly, it is preferable that the timing to start the controllingfor variably incrementing the valve operating angle and the valve liftamount on the left bank comes after the top dead center of the firstcylinder at the earliest. More preferably, the timing to start thecontrolling for variably incrementing the valve operating angle and thevalve lift amount on the left bank comes at a more delayed time afterthe top dead center, and therefore, is set at the most delayed time atwhich the valve operating angle and the valve lift amount in the intakestroke of the fourth cylinder can be increased.

To be specific, for example, a point of time that comes earlier by aresponse lag time than the opening timing of intake valves 105 at thevalve operating angle after the controlling operation for incrementingis set as the start timing of controlling for variably incrementing thevalve operating angle and the valve lift amount in the intake stroke ofthe fourth cylinder.

Incidentally, the start timing of controlling for variably incrementingthe valve operating angle and the valve lift amount in the left bank canbe set based on an angle from termination of the intake stroke of thethird cylinder.

Further, if the control for incrementing the valve operating angle andthe valve lift amount on the right bank is started simultaneously withthe controlling for incrementing the valve operating angle and the valvelift amount on the left bank, the valve operating angle and the valvelift amount in the previous intake stroke of the third cylinder areincremented to be overlapped with the incremented valve operating angleand the incremented valve lift amount in the second intake stroke of thefourth cylinder, so that a large load for driving the opening of intakevalves 105 is additionally expended at an initial period of theautomatic starting of the engine.

Therefore, the controlling for variably incrementing the valve operatingangle and the valve lift amount on the right bank is started with a timedifference from the starting time of the controlling on the left bank.If this time difference corresponds to a time for one stroke, it ispossible to avoid the increment of the valve operating angle and thevalve lift amount at least in the first intake stroke of the thirdcylinder, so that the first intake stroke of the third cylinder isexecuted in a state where the valve operating angle and the valve liftamount are small.

Namely, for the intake stroke on the right bank, the first intake strokeis executed in the state where the valve operating angle and the valvelift amount are small, and the valve operating angle and the valve liftamount are incremented to the values by which the starting of the engineoperation can be continued from the next intake stroke.

However, in the case where the load by operating actuator 17 isnegligibly smaller compared to the load for driving the opening ofintake valves 105, the controlling for variably incrementing the valveoperating angle and the valve lift amount on the bank to which thecylinder stopped in the expansion stroke belongs can be started with thestart of the automatic starting of the engine, and the valve operatingangle and the valve lift amount on the other bank can be started afterthe first intake stroke in the other bank is terminated.

Further, the control start timing for variably incrementing the valveoperating angle and the valve lift amount can be determined based on ajudgment of completion of the starting of engine 101. For example, it ispossible that at a point of time when it is judged that the enginerotating speed or an acceleration for speeding up of the engine rotationexceeds a reference value, it is judged that the starting of the engineis completed, and the control for variably incrementing the valveoperating angle and the valve lift amount is started for variable valvelift mechanism 112 on the bank to which the cylinder to be next in theintake stroke or for two variable valve lift mechanisms 112 a, 112 b atthe same time.

In this case, the control start timing at step S304 is the point of timewhen it is judged that the engine rotating speed or the acceleration forspeeding up the engine rotation exceeds the reference value.

Further, in the case where there is disposed a variable valve liftmechanism which varies an operating angle of exhaust valves 107 and alift amount thereof together with variable valve lift mechanism 112which varies the operating angle of intake valves 105 and the liftamount thereof, it is possible that the operating angle of exhaustvalves 107 and the lift amount thereof as well as those of intake valves106 are forcibly set to be small at the automatic starting of theengine, and the operating angle of intake valves 105 and the lift amountthereof start to be incremented with a time difference between those ofexhaust valves 107.

Further, the variable valve mechanism is not limited to theabove-described variable valve lift mechanism 112, and for example, maybe a variable valve mechanism which varies opening characteristics ofengine valve by switching a three-dimensional cam or a plurality ofcams. Therefore, the present invention is widely applicable to an engineprovided with a variable valve mechanism which varies an operating angleand/or a lift amount of an engine valve.

Furthermore, in an electromagnetic drive valve which drives to open orclose an engine valve using an electromagnet, it is possible to reduce aload of the electromagnetic drive valve to thereby enhance the rate ofsuccess in the automatic starting of an engine, by forcibly decreasingthe valve operating angle at the automatic starting of the engine.

Still further, it is possible to judge, based on the engine rotatingspeed, the acceleration for increasing the engine rotating speed or thelike after the automatic starting of an engine, as to whether theautomatic starting of the engine is succeeded or failed, and when theautomatic starting of the engine is failed, the starter motor isautomatically driven to thereby restart the engine operation.

Moreover, engine 101 is not limited to the V-type engine, and may be ahorizontally-opposed engine or an in-line engine.

The entire contents of Japanese Patent Application No. 2007-058958 filedon Mar. 8, 2007 a priority of which is claimed, are incorporated hereinby reference.

While only selected embodiment has been chosen to illustrate anddescribe the present invention, it will be apparent to those skilled inthe art from this disclosure that various changes and modifications canbe made herein without departing from the scope of the invention asdefined in the appended claims.

Furthermore, the foregoing description of the embodiment according tothe present invention is provided for illustration only, and not for thepurpose of limiting the invention as defined by the appended claims andtheir equivalents.

1. An apparatus for controlling a starting operation of an engineprovided with a variable valve mechanism capable of varying openingcharacteristics of an engine valve, comprising: a starting deviceconfigured to execute ignition of fuel existing in a combustion chamberof the engine in a state where an engine operation is stopped, tothereby start the engine operation; and a load controlling deviceconfigured to forcibly reduce a load expended by the variable valvemechanism at a moment of starting of the engine operation by thestarting device.
 2. The apparatus according to claim 1, wherein the loadcontrolling device continues to hold a state where the load by thevariable valve mechanism is forcibly reduced for one stroke of theengine.
 3. The apparatus according to claim 1, wherein the loadcontrolling device continues to hold a state where the load by thevariable valve mechanism is forcibly reduced up to a top dead center ofcompression stroke at the first time.
 4. The apparatus according toclaim 1, wherein the load controlling device continues to hold a statewhere the load by the variable valve mechanism is forcibly reduced untiljudgment is made that a starting of the engine operation is completed.5. The apparatus according to claim 1, wherein the load controllingdevice forcibly controls the opening characteristics such that a loadexpended for driving an opening of the engine valve is small, toforcibly reduce the load by the variable valve mechanism.
 6. Theapparatus according to claim 5, wherein the load controlling deviceforcibly controls the opening characteristics such that the loadexpended for driving the opening of the engine valve is small, when theengine operation is stopped.
 7. The apparatus according to claim 1,wherein the variable valve mechanism is comprised of a mechanism that iscapable of varying a lift amount of the engine valve, and the loadcontrolling device forcibly reduces the valve lift amount, to forciblyreduce the load by the variable valve mechanism.
 8. The apparatusaccording to claim 1i wherein the variable valve mechanism is comprisedof a mechanism that is capable of varying an operating angle of theengine valve, and the load controlling device forcibly reduces the valveoperating angle, to forcibly reduce the load by the variable valvemechanism.
 9. The apparatus according to claim 1, wherein the variablevalve mechanism is comprised of a plurality of identical variable valvemechanisms arranged to be independent from each other, and the loadcontrolling device controls the plurality of independent variable valvemechanisms, respectively, to vary the opening characteristics of theengine valves with a time difference between the plurality ofindependent variable valve mechanisms, to forcibly reduce the loads bythe variable valve mechanisms.
 10. The apparatus according to claim 9,wherein the engine is provided with two banks, each including thevariable valve mechanism, and the load controlling device is configuredto control the variable valve mechanism on each of the two banks to varythe opening characteristics with a time difference between the variablevalve mechanisms on the two banks.
 11. The apparatus according to claim9, wherein the load controlling device controls the plurality ofindependent variable valve mechanisms to vary the openingcharacteristics in which the loads expended for driving openings ofrespective of the engine valves are, respectively, small to those inwhich the loads expended for driving the openings of the respectiveengine valves are, respectively, large, with a time difference betweenthe plurality of independent variable valve mechanisms.
 12. A method ofcontrolling a starting operation of an engine provided with a variablevalve mechanism capable of varying opening characteristics of an enginevalve, comprising the steps of: judging as to whether or not there is anissuance of a request for starting the engine; igniting fuel existing ina combustion chamber of the engine, when there is the issuance of therequest for starting the engine, in a state where an engine operation isbeing stopped, to thereby restart the engine operation; and forciblyreducing a load expended by the variable valve mechanism at a moment ofstarting of the engine operation.
 13. The method according to claim 12,wherein the step of forcibly reducing the load by the variable valvemechanism comprises the steps of: judging as to whether or not there hasbeen an elapse of a period of time for one stroke of the engine fromcommencement of the starting of the engine operation; and forciblyreducing the load by the variable valve mechanism during a time durationuntil elapsing of the said period of time has elapsed.
 14. The methodaccording to claim 12, wherein the step of forcibly reducing the loadexpended by the variable valve mechanism comprises the steps of: judgingas to whether or not there has been an elapse of a period of time fromthe starting of the engine operation to arriving at the compression topdead center at a first time; and forcibly reducing the load by thevariable valve mechanism during a time duration until elapsing of thesaid period of time.
 15. The method according to claim 12, wherein thestep of forcibly reducing the load by the variable valve mechanismcomprises the steps of: judging as to whether or not the starting of theengine operation has completed; and forcibly reducing the load by thevariable valve mechanism during a time duration until it is judged thatthe starting of the engine operation is completed.
 16. The methodaccording to claim 12, wherein the step of forcibly reducing the load bythe variable valve mechanism comprises the steps of: judging as towhether or not the engine operation is stopped; and controlling thevariable valve mechanism, when it is judged that the engine operation isstopped, toward the destination that the engine valve has the openingcharacteristics in which the load for driving an opening of the enginevalve is small.
 17. The method according to claim 12, wherein thevariable valve mechanism is comprised of a plurality of identicalvariable valve mechanisms, each being independent from one another, andthe step of forcibly reducing the load by the variable valve mechanismcomprises the steps of: allowing some of the plurality of variable valvemechanisms to perform a variation of the opening characteristics of theengine valve; judging as to whether or not there is an elapse of a givendelay time from the variation of the opening characteristics of theengine; urging, after judgment of the elapse of the delay time, theother variable valve mechanisms except for the some of the plurality ofvariable valve mechanisms that have not yet performed variation of theopening characteristics, to vary the opening characteristics of theengine valve.
 18. The method according to claim 17, wherein the engineis provided with first and second banks, each including the variablevalve mechanism, and the step of allowing the some of the plurality ofvariable valve mechanisms to vary the opening characteristics of theengine valve, controls the variable valve mechanism on the first bank tovary the opening characteristics of the engine valve, and the step ofallowing, after the elapse of the given delay time, the other variablevalve mechanisms to vary the opening characteristics, allows thevariable valve mechanism on the second bank to vary the openingcharacteristics of the engine valve.
 19. The method according to claim17, wherein the stop of allowing the some of the variable valvemechanisms to vary the opening characteristics of the engine valve andthe step of allowing, after the elapse of the given delay time, theother variable valve mechanisms to vary the opening characteristics ofthe engine valve, allow the plurality of variable valve mechanisms tovary the opening characteristics such a manner that loads for drivingopening of the engine valves are changed from a small load state to alarge load state, respectively.
 20. An apparatus for controlling astarting operation of an engine provided with a variable valve mechanismcapable of varying opening characteristics of an engine valve,comprising: operation starting means for igniting fuel existing in acombustion chamber of the engine in a state where an engine operation isstopped, to thereby start the engine operation; and load-controllingmeans for forcibly reducing a load expended by the variable valvemechanism at a moment of starting the engine operation by the operationstarting means.